Polysiloxanes produced by the reaction of dialkyldialkoxysilanes in the presence of aluminum or boron halides



United States Patent POLYSILOXANES PRODUCED BY THE REACTHON F DIALKYLDIALKOXYSEANES IN THE PRES ENCE OF ALUMINUM OR BORON HALIDES George H. Wagner, Kenmore, and Charles E. Erickson, Buffalo, N. Y., assignors, by mesne assignments, to Union Carbide and Carbon Corporation, a corporation of N ew York No Drawing. Application July 26, 1949, Serial No. 106,972

2 Claims. (Cl. 269-4482) The invention relates to the anhydrous condensation of substituted silanes to form polysiloxanes. The starting materials contemplated by the invention are of the typ where R and R are alkyl, X is halogen, usually chlorine,

and one, but only one, of the numbers a, b and 0 may be zero. R" may be, for example, hydrogen or alkyl.

Obviously the sum a+b+c does not exceed 4, and is not less than 2. Examples of such compounds are HSi(OEt)2Cl, Et2Si(OEt)z, EtSi(OEt)2Cl, EtSi(OEt)Cl2, EtzSi ()Et) Cl.

On condensation, an alkyl halide is formed it halogen is present, and the Si-O-Si linkage is generated:

EtSi(OEt)Cl2- [EtSiOClli-l-EtCl If halogen is absent, a simple or mixed ether is formed:

EtzSi OEt) 2- [EtsSiO] w+ EtzO In some cases both an alkyl halide and an ether are produced:

A plurality of compounds of the type disclosed above may be conjointly condensed. Whether a single compound of this type is taken, or more than one, the reaction mixture may also contain such compounds as EtzSiClz and MesSiCl which serve to modify the product in the way discussed in connection with Example 8 below.

EXAMPLE 1 EXAMPLE 2 EtSi(OEt)2Cl (41 g.) was refluxed for 20 hours with 2 g. of AlCls producing 21 g. of white solid polymer and 11 g. of a mixture of ethyl chloride and ethyl ether. The polymer contained 30.9% C, 6.9% H and 29.5% Si. The theoretical values for [EiSiOmle are 29.6% C, 6.1% H and 346% Si.

EXAMPLE 3 EtSi(OET)Cla (49 g.) was refluxed for .18 hours with 1 g. of AlCls producing 32 g. of liquid polymer contain- 1 B. P.:127 C.

2,731,485 Patented Jan. 17, 1956 ice ing hydrolyzable chlorine (ESi-Cl), and 12 g. of ethyl chloride. This amount of ethyl chloride is quantitative for the reaction:

The chlorine content of the polymer was 34.1% as against a theoretical value of. 32.7% for a product of the formula EEtSiOCIh.

EXAMPLE 4 EtSiCla (123 g.) was refluxed with 42 g. of ethanol, ethyl chloride being evolved. The residual product (128 g.) was a mixture of EtSi(OEt)Cl2, EtSi(OEt)2Cl and EtSi(OEt)3. This mixture was refluxed for 20 hours with 2 g. of AlCis producing 72 g. of solid polymer and 40 g. of a mixture of ethyl chloride and ethyl ether.

EXAMPLE 5 Et2Si(OEt)Cl (93 g.) was placed in a stainless steel reactor with 2 g. of AlCls. Upon heating for 24 hours at 256' C., 56 g. of liquid polymer and 20 g. of ethyl chloride were formed. The liquid polymer contained the cyclic trimer hexaethylcyclotrisiloxane, the cyclic tetrarner octaethylcyclotetrasiloxane, and other liquid polymers with an average molecular weight greater than 500, a typical reaction being:

EtzSi OEt) Cl EtzSiO ax-l-EtCl EXAMPLE 6 To cc. of HSi(OEt)2Cl was added 0.1 g. of AlCla, and the mixture was heated to reflux (about C.) for 2 hours. thyl chloride and ethyl other were evolved during the refluxing, and a white solid was formed which was found by analyses for H, Si and C to have essentially the empirical formula [HSlO1.5]:c. it was evidently formed by the reaction:

HSi(OEt)2Cl- [HSiOrshj-l-EtCl-I-EtzO EXAMPLE 8 EtzSiCla (0.30 mol), Et2Si(OEt)a (0.30 mol), and 2 g. of AlCls were heated at 250 C. for four hours in a stainless steel reactor. The maximum pressure developed was 5% p. s. i. gauge, and '73 g. of product was obtained. A fractional distillation of this material is shown in an nexed Table Vll.

Several other reactions of this type were conducted under conditions which are summarized in Table The results of fractional distillation of these reaction products are shown in Tables ii to IX. No attempt was made to collect the ethylchloride or ethyl ether during these fractionations. When the composition of the products is discussed hereinafter, only the polymeric products are referred to.

it will be noted that boron trichloride was used in run 27 where reaction was obtained at. 205 C. No reaction was obtained under the same: conditions at C. The purpose of the remaining experiments listed in Table I was to show the eflect of the proportions of the two reactants, EtsSiClz and EtzSi(0Et)z, and also the effect of the presence of the monofunctional compound MesSiCl on the products obtained. This will be discussed below.

' aethyltrisiloxane.

When equal molecular quantities of EtzSi(OEt)z and EtzSiClz react, the main reaction may be represented by:

xEtzSi (OEt) 2+xEtzSiClrr [EtzSiO 250+2XElCl (a) 4 weight products from a large amount of MeaSiCl and a small amount of Et2Si(OEt).2. The incidence of a considerable amount of materials boiling above hexarnethyl-3,3-diethyltrisiloxane, and especially the forma- The q d Product Should be P p y cyclic Compounds 5 tion of hexamethyldisiloxane in this reaction are indicative of the general formula (Et2SiO)2 if the reaction is comf h f ll i type f h e; plete. Incomplete reaction would give compounds of the general formula EtlIEtzsiOlzxCl. These two points -Si0Et+ gC1s-Si01+- S i0Et (0) appear to be borne out by run 25 and run 27 (Table I) each of which employed equimolar proportions of re- This type of exchange is necessary to explain the foractants. It will be noted that the products of run mation of l,3-dichlorotetraethyldisiloxane in run 27 (Table VII) contained a large amount of cyclic tetramer (Table I and Table IX). Equation d may be considered and that, in general, the products are low in chlorine, a complication of the general reaction presented here i. e., low in EtEEtzSiOlnCl. Run 27 gave products conso far as predicting the nature of the products is concerned.

Table I Reactants Reaction Pressure Product E2 1 Diethyl- Diethyl- Catalyst g 2 1 (p. s. 1., Weight dichlorodiethoxy- Hours max.) (Grams) silane silane (M015) (M015) 1 In run 10, 0.0 mol of MezSiCl was included with the reactants, while in run 17, 0.046 m0 ofMesSiC1 was used.

2 N 0 reaction.

taining considerable chlorine (Table IX) which is ascribed to incomplete reaction resulting from the use of a lower reaction temperature.

Runs 22, 23, and 24 of Table I illustrate this point.

The

high chlorine content of the products is to be noted in these cases (Tables IV, V, and VI) as is the isolation of 1,3-dichlorotetraethyldisiloxane and 1,5-dichlorohex- The chlorine content of the products from run 24 is low because only a slight excess of EtzSiClz was used in this case. Some of the cyclic tetramer was formed and was isolated in the fractionation.

With an excess of EtzSi(OEt) 2, the following reaction should prevail:

Run 26 (Tables I and VIII) is an example of this type. The analyses are not sufficient to show the validity of Equation 0 except that the products are low in chlorine. It will be noted that some cyclic tetramer formed.

Run 17 (Tables I and III) employed a small amount of the monofunctional MeaSiCl along with the Et2Si(OEt)2 and EtzSiClz. The elfect of the mono functional material, as is clearly shown by comparing the products of this run (Table III) with the products of the other runs, is to increase the molecular weight of the products. In this run 66% of the polymeric products had molecular weights of from 716 to 896. This is a larger amount of higher molecular weight material than was obtained in any of the other experiments, and is believed to be due to the formation of products of the general formula, Me3Sl(Et2SiO)xCl, MeaSi(EtzSiO)xOEt, and

MesSi(Et2SiO )xsiMes in preference to cyclic structures.

Run 16 demonstrates the formation of low molecular Table II FRACTIONATION OF PRODUCTS FROM RUN 16 [Charge=83.5 gJ

- Hydrolyz- Roi-1mg Pressure able Assumed Fraction P ollli, Grams Chlorine Product percent am. 14 atm, 13 hexamethyldisiloxane. 90 1 90 4 90-64 3 64 7 hexamethyl- 3,3-diethyltrisiloxane. 64-18 2 2.26 18 4 4.52 18-9 9 1.18 3 8 1.94

Table III FRAGTIONATION OF PRODUCTS FROM RUN 17 [Oharge=80 g.]

Hydrolyz- Bol-hng Pressure able M01 Assumed 8 6 mm. Grams Chlorine, Wt Product percent (F82 3 3 82-113 3 2 are 2 a 127 129 3 9.5 1144 III: cyclic 129-148 a 2 2.01 148-155 3 1 156468 3 13 7.06 716 35.5 6.07 895 Table IV Table IX FRAOTIONATION OF PRODUCTS FROM RUN 22 FRACTIONATION F PRODUCTS FROM RUN 27 {C11argo=130 g.] [Charge- 97 g.]

. Hydro- Bolling Pres- E d Fraelyzable Moi. Assumed B 11 1 5 y m Point sure Grams F g ms 1 bl M l A d t on 1 1 Oh rec yzn e 0.. ssume 1 O. mm. 53 5 Wt Product tron 29 6 gig Grams Chlormo, Wt. Product percent 4550 45 9 42 31 dlgitilgtllchloro 44 82 40 7 2 50410 9 1 10 2 82- 1 1 3 90-91 9 25.5 27.10 1,3-dichlorotetra- 89-98 9 8 impure eth ldisiloxchlorotetra' y BthYIdISIIOX- 1- 3118. 3 .25 3 i Q 2 14.91 137-136 9 22.5 19. 57 1,5-dich1orohexa- 9 2 1328 1 ethgltrisilox- 9 16 16-09 lg g g -3;- 1 8118. g 32:14; 9 7 17.04 gslllgltrlsrloxi5; 160 9 ,2 577 7 142-154 9 s 5 as impurecyclictets 151 160 9 s 11 93 Hamel" 1 Theoretical ch1ori11e=45.17. "Theoretical chl0riue=27.47;. 20 672 3 Theoretical chlorine=19.65%.

Table V 'lheoretiosl chlorine=27.4%.

2 11 FRACTIONATION OF PRODUCTS FROM RUN 2a Theoretwal 0 10mm 19 65% [Oh =115 EXAMPLE 9 Eydm 25 EtOSiCls (280 g.) was refluxed for 4 hours with 3 $25 Grams Mable MOL Assumed g. 0f AlCI 3. When evolution of EC] had ceased, there $1011 a i g f. Product remained 1n the reactlon vessel 180 g. of polymer. The

p reaction is represented by the following equation: 23-53 8 5 xEtOSiC12- xEtCl+ [ClzSiOh M2 1115 e-g i c l r The A1013 was boiled out of the siloxane at 250* c. 5 g. leaving a blackish viscous material which reacted with 4 92-135 s 1.5 phenol to form a diphenoxypolysiloxane. The quantity 5 EH45 8 19 1720 fi I of phenol reacting confirmed the formula [01281011 for at s 'ltris 10x h d ane. t e VlSCOllS pro uct. 6 145-105 8 5 Res 50 1M2 591 i What 1s claimed 1s:

1. A process for preparing polysiloxanes which conggfigg ggggi cglgg gfigg; sists of heating substituted silanes of the type:

Table VI R"2 1( R 2 FRAGTIONATION 0F PRODUCTS FROM RUN 24 40 where R and R" are alkyl radicals, in the presence of a [Oharge=79 g1 catalyst taken from the group consisting of the halides Hydrchm of aluminum and boron to a temperature of above about Fraction ilg g Pressure, Grams able M01, Assumed 300 C. to evolve an alkyl ether and recovering a siloxane 1 2 9 2 Pmdm polymer from the reaction product.

2. A process for preparing polysiloxahes which consists of heating substituted silanes of the type:

Where R and R are ethyl radicals, in the presence of a catalyst taken from the group consisting of the halides cyclic tetramer.

eemcow an H mroongwg- Table VII of aluminum and boron to a temperature of above about FRACTIONATION 0F R DUC S FROM R 25 300 C. to evolve an ethyl ether and recovering a siloxane [Gharge=73 g.] polymer from the reaction product.

. H dr 1 Fraction 3 Pressure Grams y l y M01. Assumed 55 References Cited in the file of this patent a 0. mm. g l p gg, Product UNITED STATES PATENTS 2,485,928 Servais Oct. 25, 1949 0-127 8 L5 2,618,646 Hatcher et a1. Nov. 18, 1952 .47

g 13. ifiggf o0 FOREIGN PATENTS 33' 4'85 678 476,174 Belgium Oct. 31, 1947 478,117 Belgium Jan. 31, 1948 Table VIII FRAGTIONAIION 0F PRODUCTS FROM BUN 2s OTHER REFERENCES [Qharge=.g5 g 5 Calmgaert: Jour. Am. Chem. Soc., vol. 62 (1940), pages 1107-4110. ydrolyz- Volnov: Jour. Gen. Chem. U. S. S. R. vol 17 B 1111 s 1 0 Grams 01.15318, 5t.- stszt pages percent Dolgov: Jour. Gen. Chem, U. S. S. R., vol. 18

(1948), pages 1293-4296. 1.. 0-109 9 1.5 2-.- 109-123 2 2 0.6 a-.. 123-149 a 2.5 4.31 cyclic 149-147 8-3 12.5 0.53 tetramer. 5 147458 a a 1. 23 Ros 27 3.39 735 T 

1. A PROCESS FOR PREPARING POLYSILOXANES WHICH CONSISTS OF HEATING SUBSTITUTED SILANES OF THE TYPE: 